What Prop? for my Mercruiser

[jshigman1]

I just bought my "new" used boat and cant read on the prop what pitch ect... I would like to buy a<br />backup. My boat is a 79 rinker with a 120 mercruiser in her. Can anyone point me in the right direction in what size prop to buy? Also<br />i have another? about what rpm should she be turning and aprox. at what speed? I guess what i am trying to say is what will the little 4 banger push this boat at top sped about? I havent had her in the water yet is why i am asking, just curious.

 

[ziggy]

Re: What Prop? for my Mercruiser

james O. the clymers book says wot is 4200-4600 rpm for a 181 cid 4-cyl. no idea how fast that will be. i'd think every boat would be a bit different depending on many things for top speed. my 165 in a 16' trihull does about 39ish. not to speedy. <br />do a search on props here on iboats, you'll have days of reading. the mercrusier web site has a real good discription of what props are about. i'm understand ya wanting a second prop. i want one too. but i'm waiting to see what's wrong with my boat this season before i get a second prop. who knows, maybe i need a new engine and don't know it yet. aslo you'll need to know yer wot rpms i'd think before gettin a new prop (time to launch her). and you'll still need to know the pitch of what ya got too, so ya can make a decision on what kinda new prop ya will want to get. just my 1 cent.... happy boating

 

[achris]

Re: What Prop? for my Mercruiser

Hi JamesO,<br /><br />The spec for the 153 cu. in. engine (that's what your 120 hp is) is 3900-4300rpm.<br /><br />The 181 cu. in. is the old 140hp and that one is 4200-4600.<br /><br />Because of the poor quality fuels they are serving up to us these days, I'd be propping it as close to the top (4300rpm) as possible. It doesn't hurt to go a little bit over either. Mine's specced at 4400-4800 (V6) and I'm pulling 5000 on a good day. <br /><br />Chris................

 

[ziggy]

Re: What Prop? for my Mercruiser

twice tonight, i'm obviously still learning to read, geeze, sorry for the non pertentant info. as i re read my clymers, achris has got it right for sure.